Well, it's simple linear motion. Unless there is a specific reason, I'm not sure why you can't go without the loop. Since Particular is fully 3D, the particle field would look differently, anyway from other cam angles. If you need it looping, it would probably have to be faked somehow by freezing the physics time factor and move the paticle cloud emitter in 3D and jumble it up with turbulence.... Mmh.
i'd like to make it seamless 'cause i'm using it in a motion Menu for Encore.I'll give it a try.
Is there no solution to make it loopable without making 100's of copies of the same layer?
Let's assume there is no cam animation.
Nope. Particular uses correct physical evaluation of the particle properties which means it doesn't recycle data. Therefore it never loops. Your setup looks simple enough to mimic with other tools like CC Particle World or CC Bubbles, so maybe give that a try.